Very specifically, the issues that were causing the zombie slow down which resulted in them getting stuck has been fixed.

I believe I have still observed some zombies still experiencing slow down. However, they do not get stuck, and it's no where near as extreme as it was. I'm going to look into it further once I've finished testing, and released an update I've had on hold since I discovered the original bug.

You can consider WZ fully functional again in B42.
Praise TIS.